A/T - High Pitch Whine at Highway Speeds

Number: 86-173

Section: 7A

Date: OCT., 1986
Subject: HIGH PITCH WHINE AT HIGHWAY SPEEDS

Model and year: 1985-86 NOVA WITH AUTOMATIC TRANSMISSION
TO: ALL CHEVROLET DEALERS

Some of the subject vehicles may exhibit a high pitched whine at highway speeds. This condition occurs in any gear and is most apparent during acceleration and coast down maneuvers at these speeds.

The condition is caused by the constant mesh counter gear set located at the extreme outboard and (left hand side of car) of the transmission. This noise is transferred through the speedometer cable into the passenger compartment. This noise does not indicate a reliability or durability concern with regard to the transmission.

A new speedometer cable design incorporating a sound isolation feature has been released, this is a two-piece cable design and is available from WDDGM by ordering both parts: 94844466 speedometer cable-lower; 94844467 speedometer cable-upper.

NOTICE: BOTH PARTS ARE REQUIRED TO REPLACE THE EXISTING ONE-PIECE CABLE.

Revised counter gear tooth geometry has also been developed to reduce gear noise, a kit is available from WDDGM by ordering P/N 94844514.

Both of the above design changes are incorporated in vehicles produced after VIN serial number (last 6 digits) 190000 for USA and 253500 (Canada) during the 1986 model year (date Code G).

To correct this condition on complaint vehicles built prior to these VIN breakpoints the following stops should be carried out:

1. To remove existing one-piece speedometer cable, see illustration and instructions for procedure.

2. Install new upper and lower cables after first connecting the two parts together at the connector. The connected speedo cables can be installed by reversing the procedures for removing the original cable.

3. Evaluate vehicle for existence of complaint condition and compare with original complaint level. If a satisfactory level of improvement has been achieved, no further changes are required.

NOTICE: TESTING HAS SHOWN THAT THE TWO-PIECE SPEEDO CABLE WILL SATISFACTORILY CORRECT THE MAJORITY OF COMPLAINT VEHICLES. IN THE EVENT THAT A SATISFACTORY LEVEL OF PERFORMANCE HAS NOT BEEN REACHED, PROCEED TO STEP 4.

4. Replace counter-gear set with parts contained in new counter-gear kit using existing shop Manual procedures.

Use applicable Labor Time and Operation Number.

NEW CABLE INSTALLATION:

1. Remove 4 screws - pull hood (retained by 2 clips).
2. Disconnect RWD switch connector.
3. Remove inst. cluster - remove 4 screws (A) pull cluster forward - release speedo cable from speedometer.
4. Release speedo cable at transmission & remove cable.
5. Install new cable in reverse order.